This invention relates to an apparatus for cutting metal bars, such as bars used during construction to reinforce concrete, generally known as rebars, and in particular to such a device which is portable and can be used on the ground at construction sites.
U.S. Pat. No. 4,594,875, issued June 17, 1986 to the inventor hereof, the disclosure of which is incorporated herein by reference, discloses and claims an improved rebar bending machine which is lightweight, hand operated and adapted to be used in the field by a single person. It has a laterally stabilized, elongated base and, mounted to the base a pair of spaced apart forming posts which straddle a slide mounted pair of lugs that form between them a groove into which rebar to be bent is placed. The slide is movable in an elongated guideway in a direction perpendicular to a line interconnecting the centers of the forming posts so that the groove defined by the lugs can be moved from a first position, at which a rebar placed in the groove is substantially tangent to the peripheries of the posts, past the line interconnecting the post centers, to a second position on the other side of the posts. In the course of this linear movement of the grooves a bend is formed in that portion of the rebar disposed between the lugs. Depending upon the length of travel of the lugs a bend of less than equal to or greater than 90.degree. is formed in the rebar although 90.degree. bends are by far the most common.
That patent further discloses to generate the relatively large bending forces with an elongated handle that is pivotally attached to the base. Suitable linkage connected to the handle and the slide translates the pivotal handle movements into linear slide motions.
To minimize the weight of the bending machine, and to maximize the bending force, the slide, post and linkage are arranged so that the slide does not travel substantially more than the distance it must travel to effect the greatest bend in the bar typically a bend of not more than about 120.degree.. In this manner, the overall length of the device in general and of the slide, base and guideway in particular can be minimized, which saves weight, labor and costs. Within a given size and configuration of the machine, the bending force that can be generated with the manually operated handle can be maximized. An effective, high speed and accurate bending of the rebar is thus possible with the device of that patent.
Bending machines constructed in accordance with the above-mentioned patent have been on sale for more than a year and have met with exceptional success. It is believed that the success is to a large extent attributable to its compact size, relatively low weight and to its easy operation even on the uneven ground frequently encountered at construction sites.
At construction sites, it is frequently necessary to cut a bent or straight rebar. Although many rebar cutters are known and available, they are usually heavy, stationary, and/or machine-operated devices which, not infrequently, are relatively remote from the place where a rebar is being bent with a bending machine of the type disclosed in the '875 patent. Thus, the bar to be cut must be hand-carried to the cutting machine, wherever it may be located, cut, and then returned to the location where it will be used. This is time-consuming, for large diameter and/or long rebars constitutes heavy physical labor, and is, therefore, costly.
U.S. Ser. No. 059,703, now U.S. Pat. No. 4,798,078, the parent of the present application, discloses a machine for cutting rebar adapted to be attached to the improved rebar bending machine disclosed in the '875 patent discussed above. This cutting machine has a pair of closely adjacent cutting discs, one stationary and the other pivotal relative thereto, both of which include a peripherally open slot into which the rebar to be cut can be placed. The discs are mounted in a frame, preferably defined by two spaced apart, rigidly interconnected plates which have an upright portion through which a pivot shaft for the discs extends and a relatively horizontal portion which is used to connect the cutter with the rebar bending machine of the '875 patent.
In use, a rebar is placed in the aligned slots. An operator lowers the handle to move a slide and engage the roller of an arm connected to one of the cutting discs, causing relative movement of the discs and a corresponding rotational offset of the two slots of the discs, thereby severing the rebar. This cutter is a significant improvement over the prior art, allowing rebar cutting at the site with a simple, rugged, lowcost device. However, a relatively large force is still required to rotate the disc especially when cutting larger diameter rebar. The total force required to cut the rebar must be applied in one stroke. Thus, relatively heavy physical labor is still required. In particular, at times so much force must be applied to the handle that slightly built workers might have insufficient weight to push the handle down.